The Prime Minister’s unprecedented cash splash paves the way for construction to start as early as 2020, once one of four routes between the city and Tullamarine is chosen.

The PM wrote to Premier Daniel Andrews last night, asking for a 50-50 funding split to build and own the “iconic piece of infrastructure”.

“What we’re putting to the state government is we will own and build the rail link together as partners,” Mr Turnbull told 3AW.

“We’d invest up to $5 billion for a 50 per cent share.

“$5 billion is the sort of money and leadership to get this started.”

To date, the only way for travellers to exit Melbourne airport — apart from flying — is by road. Picture: Jason EdwardsMr Turnbull denied squabbling between the federal and state governments could delay the project.

He said a move to begin construction of the project by 2020 is not totally off the cards but was “ambitious”.

“I wouldn’t say it’s not on,” he said.

The Andrews Government cautiously welcomed Mr Turnbull’s announcement and financial backing and the fact that the Commonwealth has not tried to dictate a preferred route.

Public Transport Minister Jacinta Allan said the state would continue the planning work underway into the best model and route for the line.

“It’s good that the Prime Minister has finally found Victoria on the map,” Ms Allan said.

“We have already committed to the rail line to the airport and the detailed planning work is already underway and the federal government is involved in that.”

Private investment might also be an option, to meet a price tag of up to $15 billion.

The Herald Sun can reveal that the $5 billion contribution to the city-shaping project, creating thousands of jobs, will be the single largest infrastructure investment in next month’s federal Budget.

The rail link will likely offer both an express service and services stopping at current or new stations.

“The time for talk is over,” Mr Turnbull told the Herald Sun.

“There have been countless reviews, reports and recommendations, but Melbourne is still waiting for a service almost all of the world’s great cities take for granted. With our commitment of up to $5 billion ... we are guaranteeing the Melbourne airport rail link will be built.”

It is estimated 60 million passengers a year will use the airport by 2030.

The federal government today unveiled four options for a link, including above-ground and underground tracks.

Its preferred routes through Maribyrnong would link to Highpoint shopping centre and Victoria University, and open up a major new suburb of 6000 homes on former defence land.

SCROLL DOWN TO SEE THE PROPOSED ROUTES

Traffic banked up at Essendon on the Tullamarine freeway. Picture: Nicole GarmstonThe Herald Sun can also reveal:

EACH route would likely end in a new underground airport station and connect to the city either directly through Southern Cross, around the City Loop, or into the new Metro Tunnel.

A BUSINESS case will, by September, present options for new railway stations in Melbourne’s inner northwest.

MORE infrastructure cash for Victoria will also follow, after years of criticism about a lack of federal funding.

Mr Turnbull will today encourage Mr Andrews to match his commitment by injecting the $2 billion Victoria receives from selling its share of the iconic Snowy Hydro scheme into the airport rail project.

The Premier promised last November that construction on the rail link would be under way within the next decade, but the government has argued a train can’t run until the Metro Tunnel opens in 2026.

About 60 million passengers a year will use the airport by 2030.The business case will include options for unsolicited bids or other private sector contributions. The Commonwealth is keen to capitalise on the commercial value of a new suburb within 10km of the city.

Treasurer Scott Morrison said: “With this new investment, the Commonwealth now has $17.5 billion committed to transport infrastructure projects in Victoria — including the $3 billion put aside for the East West Link.”

Federal government MPs from Victoria have long lobbied the PM for more money for the state.

“We know getting people to the airport faster and getting cars off the Tullamarine Freeway has flow-on benefits across the city,” Victorian minister Kelly O’Dwyer said.

Opposition Leader Bill Shorten has backed the link.

FOUR WAYS TO BEAT GRIDLOCKA NEW underground station at Melbourne airport is expected to be built to provide travellers with easy access to the long-awaited train service to and from Tullamarine.

The Herald Sun can reveal four possible routes for the rail link are on the table. A $30 million business case will assess each option by September.

All routes are likely to enter Tullamarine via a tunnel and into an underground station, to avoid worsening congestion in an already chaotic forecourt used by cars, taxis, ride-sharing services and buses.

Three of the four options could see the airport train run around the City Loop, stopping at Flinders St, Southern Cross, Melbourne Central and Parliament stations.MELBOURNE AIRPORT SLASHES PARKING FEES

The Flemington and Albion East routes.

The Craigieburn and direct tunnel routes.The planning process is considering all options for access to the city, so the route could potentially take travellers all around the CBD. A direct connection into Southern Cross, long the popular option, is also still on the cards.

The fourth route, known as the Albion East option — which the Herald Sun understands is preferred by the state government — would enter the CBD through the Metro Tunnel, not due to open until 2026.

Once the business case is ­finalised, the state and federal governments will face a choice between four options with vastly different strengths and weaknesses.

The Flemington and Direct Tunnel routes are believed to be preferred by the federal government because both options would open up access to a new suburb to be built on the 127ha former defence site in Maribyrnong.

The land, on the banks of the Maribyrnong River, is less than 10km from the city centre and could fit up to 6000 new homes and provide for thousands of new jobs.

A new suburb is to be built on a former defence site in Maribyrnong. Picture: Alex Coppel.Those two options would be the most expensive, because they require extensive tunnelling, but they would also be the most direct.

While no decisions have been made on new stations, one would likely be at Highpoint shopping centre.

A direct route through ­Maribyrnong without stops has also not been ruled out.

The Albion East alignment which has long been touted for a Tullamarine airport rail link, would be cheaper because it would be almost entirely above-ground and use some existing tracks.

The Craigieburn link would be a cheaper option, but it appears less likely to be chosen, because it stops at least 13 times along the existing railway line running through Melbourne’s north.

A decision would also have to be made on whether to run purpose-built airport trains with luggage racks or whether airport travellers would just board normal commuter trains running along that line.